Wah How to use "You are to"

We can use Subject + Be + To when we are talking about responsibilities or duties.
This form has the same meaning as Be supposed to.

• My mom told me that I was to clean up the house before she was back. (I was supposed to clean up the house.)
• My boss says that John is to finish the job by Friday. (John is supposed to finish the job by Friday.)
• The doctor said that I was to start exercising. (I was supposed to start exercising.)
• Employees are to wash their hands after using the toilet.
• Jane is to present her report first.
• My children are to read a book before bed every day.
• The security guards are to ensure that everything is alright.

The police officer told her that she was to drive slowly.